Gelle's test is for

Gelle's test: It is also a test of bone conduction and examines the effect of increased air pressure in the ear canal on hearing. Normally, when the air pressure in the ear canal is increased in the ear canal by Siegel's speculum, it pushes the tympanic membrane and possible inwards raise the intralabyrinthine pressure and cause immobility of basilar membrane and decreased hearing, but no change in hearing is observed when the ossicular chain is fixed or disconnected. Gelle's test is performed by placing a vibrating tuning fork on the mastoid while changes in air pressure in the ear canal are brought about by Siegel's speculum. Gelle's test is positive in normal persons and in those with sensorineural hearing loss. It is negative when the ossicular chain is fixed or disconnected. It was a popular test to find out stapes fixation in otosclerosis. Ref: Diseases of EAR, NOSE and THROAT by PL Dhingra; 7th Edition; page no.24,25